The present invention relates to a substrate having a plurality of light-emitting elements such as LEDs mounted thereon and to a lighting apparatus having this substrate incorporated in an apparatus main body.
Recently, lighting apparatus which uses a plurality of light-emitting elements such as LEDs as light sources have been developed. For lighting apparatus of this type, a demand of a high output is increasing, and there is a tendency that the number of light-emitting elements employed is also increasing.
The plurality of light-emitting elements are mounted on the substrate and incorporated into an apparatus main body. The substrate is subjected to heating and cooling by heat from the light sources as the lighting apparatus is turned on and off, and they repeatedly undergo thermal expansion and thermal contraction. For this reason, the substrate is easily warped or deformed due to heat.
Heretofore, to avoid such thermal deformation of the substrate, the substrate is appressed against the apparatus main body and both members are fastened and fixed at a plurality of positions by using a plurality of screws. As a result, tight connection of the substrate with respect to the apparatus main body can be improved, and heat of the substrate can be excellently conducted to the apparatus main body, thus suppressing warpage or deformation due to heat of the substrate.
However, when the substrate is screwed into the apparatus main body at the plurality of positions as described above, the substrate gets distorted and deformed when the substrate thermally expands and thermally shrinks between the fixing positions. When the substrate is deformed in this manner, a soldered portion to which an electronic component is secured may be cracked or the tight connection of the substrate with respect to the apparatus main body may be degraded in some cases. When the tight connection of the substrate is degraded, heat radiation of the substrate cannot be sufficiently performed, and the substrate is further deformed.
On the other hand, in the field of manufacture of a thinned semiconductor package, there is known a structure where a reinforcing member is disposed to an upper side of a substrate to surround a semiconductor element mounted on the substrate and this reinforcing member is sealed together with the semiconductor element by a sealing member in order to avoid warpage, breakage due to insufficiency of strength, a mounting error, and others (see. JP-A 2006-228932 (KOKAI)).
However, in the structure depicted in this Patent Document, when linear expansion coefficients of the substrate, the reinforcing member, and the sealing member are different from each other, warpage or deformation occurs in the substrate increasingly. Therefore, selecting materials for the respective members is difficult. Further, since the reinforcing member must be prepared separately from the substrate, the number of components is increased, and the number of manufacturing steps is also increased.
If the reinforcing structure disclosed in this Patent Document is adopted for the substrate in the lighting apparatus having the plurality of light-emitting elements mounted thereon, thermal deformation of the substrate cannot be effectively avoided.